Tooth morphology elucidates shark evolution across the end-Cretaceous mass extinction

Sharks (Selachimorpha) are iconic marine predators that have survived multiple mass extinctions over geologic time. Their prolific fossil record is represented mainly by isolated shed teeth, which provide the basis for reconstructing deep time diversity changes affecting different selachimorph clades. By contrast, corresponding shifts in shark ecology, as measured through morphological disparity, have received comparatively limited analytical attention. Here, we use a geometric morphometric approach to comprehensively examine tooth morphologies in multiple shark lineages traversing the catastrophic end-Cretaceous mass extinction — this event terminated the Mesozoic Era 66 million years ago. Our results show that selachimorphs maintained virtually static levels of dental disparity in most of their constituent clades across the Cretaceous–Paleogene interval. Nevertheless, selective extinctions did impact apex predator species characterized by triangular blade-like teeth. This is particula...

鲨形总目（Selachimorpha）即鲨鱼，是标志性的海洋捕食类群，在地质历史时期历经多次大灭绝事件仍得以存续。其大量留存的化石记录主要以脱落的孤立牙齿为代表，这些牙齿为重建不同鲨形类支系的深时多样性变化提供了核心依据。与之相对，通过形态差异度（morphological disparity）量化的鲨鱼生态对应转变，仅获得了相对有限的分析关注。本研究采用几何形态测量法（geometric morphometric approach），全面检视了跨越白垩纪末期灾难性大灭绝事件——这场于6600万年前终结中生代（Mesozoic Era）的地球灾变——的多个鲨形类支系的牙齿形态。研究结果显示，在白垩纪-古近纪（Cretaceous–Paleogene）过渡区间内，绝大多数鲨形类支系的牙齿形态差异度基本维持稳定水平。不过，选择性灭绝事件确实对以三角形刃状牙齿为特征的顶级捕食者类群造成了显著冲击。此尤为